Justification:Lissodelphis borealis is widespread and abundant, with population estimates in the high tens to low hundreds of thousands throughout their North Pacific range. High levels of bycatch during the 1970s and 1980s are estimated to have reduced their population size within the last three generations by an unknown amount, but the most realistic scenarios suggest the decline was 30% or less. The primary threat to this species (high seas driftnet fishing), which caused the population decline, has largely been eliminated since 1993.

The Northern Right Whale Dolphin is found in deep, temperate waters of the North Pacific Ocean, between about 30°N and 50°N.

The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states.

Estimates of abundance are available for a subset of the range of Northern Right Whale Dolphins. Across the oceanic North Pacific, Buckland et al. (1993) estimated 68,000 (CV=71%) and Miyashita (1993) estimated 307,000 Northern Right Whale Dolphins, with wide confidence limits, from sighting data, whereas Hiramatsu (1993) estimated about 400,000 dolphins for the same region based on bycatch data. All estimates have high uncertainty, and Buckland (1993) considered the two higher estimates to be positively biased. In the eastern North Pacific, the distribution of this species has been documented to vary seasonally (Forney and Barlow 1998), and abundance estimates along the U.S. West Coast have ranged from about 9,000 to 21,000 dolphins (Forney 1995, Barlow and Forney, in press). The average abundance in this region during 1996-2001 was estimated to be about 11,000 (CV = 26%); Barlow and Forney, in press).

The habitat of this species includes deep oceanic waters from the outer continental shelf across the temperate North Pacific. They are sometimes seen nearshore, especially where deep water approaches the coast (such as underwater canyons), and apparently prefer "coastal-type" waters in the California Current system (see Jefferson et al. 1994). Ferrero (1998) observed in the central North Pacific that sea surface temperature was the most influential habitat parameter, with L. borealis occupying warmer waters than either Phocoenoides dalli or Lagenorhynchus obliquidens.

Groups of Northern Right Whale Dolphins mixed with other marine mammals, especially Pacific White-sided Dolphins (with which they share a nearly identical range) and Risso’s Dolphins, are not uncommon (Baird and Stacey 1991).

Although market squid and lanternfish are the major prey items for Northern Right Whale Dolphins off southern California, a variety of other species are taken by this species throughout the range. These include various species of cephalopods, hakes, sauries, and several species of surface and midwater fishes.

Lissodelphis borealis experienced very high levels of fishery-induced mortality in international high-seas, large-scale driftnet fisheries, from about 38°N to 46°N and 171°E to 151°W. Assessing the impact of this mortality is complicated by the possible existence of a coastal population off California and the Pacific Northwest that is separate from offshore populations that were subject to high levels of bycatch (Dizon et al. 1994). Total numbers killed by the North Pacific squid driftnet fleets of Japan, Taiwan, and South Korea in the late 1980s were estimated at about 15,000–24,000 per year, and this mortality is considered to have depleted the oceanic population by an unknown amount. Using a variety of assumptions about population estimates, growth rates, and bycatch levels, Mangel (1993) presented a range of analyses that indicate declines of less than 30% were most likely, although more severe declines of up to 45–75% could not entirely be ruled out under certain scenarios, including a few biologically unrealistic ones. The UN moratorium on large-scale high-seas driftnets that came into effect in 1993 relieved this pressure to a considerable extent, but the continued use of driftnets to catch billfish, sharks, squid, and tuna inside the exclusive economic zones (EEZ) of North Pacific countries and some continued illegal fishing on the high-seas results in the killing of unknown numbers of Northern Right Whale Dolphins each year.

Incidental catches have also occurred in Japanese and Russian purse seines, Japanese salmon driftnets, and U.S. shark and swordfish driftnets. Small numbers have been killed in commercial and experimental salmon drift-net operations in the western and central Pacific (Jefferson et al. 1994). An estimated 386 Northern Right Whale Dolphins were killed between 1990 and 2002 in U.S. driftnets targeting sharks and swordfish off the California, Oregon and Washington (Julian and Beeson 1998, Carretta et al. 2005). A short-lived Canadian experimental driftnet fishery for flying squid killed a total of 13 in 1986 and 1987 (Jefferson et al. 1994). Northern Right Whale Dolphins have also been observed entangled in net debris in the western Pacific. The total reported take of Northern Right Whale Dolphins by Japan in 1987 was 261 individuals, of which 254 were discarded as bycatch (Government of Japan 1989).

Northern Right Whale Dolphins have never been subject to extensive directed hunt, although they have sometimes been taken in Japan’s small-cetacean fisheries. In the western Pacific, coastal fisheries off Japan have taken them for many years, with 465 reported killed in the harpoon fishery in 1949. Although this fishery mainly targets other small cetaceans, Northern Right Whale Dolphins continue to be taken (Jefferson et al. 1994).

The most significant conservation measure for this species was the United Nations (U.N.) moratorium on high-seas driftnet fishing. In the eastern North Pacific, the U.S drift gillnet fishery has been required since 1996 to use acoustic warning devices (pingers) to reduce cetacean bycatch, although low levels of bycatch of Lissodelphis borealis have continued (Carretta et al. 2005).

In-Place Research, Monitoring and PlanningIn-Place Land/Water Protection and ManagementIn-Place Species ManagementIn-Place Education Included in international legislation:Yes Subject to any international management/trade controls:Yes

Hiramatsu, K. 1993. Estimation of population abundance of northern right whale dolphins in the North Pacific using the bycatch data from the Japanese squid driftnet fishery. International North Pacific Fisheries Commission Bulletin 53(3): 381-386.